What's the cheapest way to travel from NYC to PHL via amtrak 3 times a week?

I am commuting from New York Penn Station to Philadelphia 30th st. station 3 times a week. What's the cheapest way? Is there a weekly pass that I can purchase?

Amtrak is expensive and has limited service.

Most cheapest way will be:
Put $2.00 and PATH Fare $1.50 (March 2nd, $1.75).
Take downtown A express to Chambers St, go follow PATH and paid $1.50/$1.75 on PATH to Newark Penn Station.
Than next, buy Weekly Pass from Newark Penn Station to Trenton for $78.50.
With your pass, you could also use on RiverLine $1.35. Weekly pass does not have to be validaded.
Next, take RiverLine to Walter Rand Transportation for $1.15 PATCO to Philly, then purchase 7-Day Pass for SEPTA Subway/Trolley/Bus to 30th St Station.
MOST CHEAPEST OPTION.
SEPTA Regional Rail offers TrailPass based on fare zone you go.

Check at the ticket office. They can tell you about any discount ticket deals they might have. Have a great day!

I assume that you are aware of the N.J. Transit/Septa possibility for travel from NYC to Phila, but if you take NJ transit to Trenton and then Amtrack to Phila, you loose much less time, and it may not be a bad compromise of price.

NJ Transit offers various 'package deals'. I am nnot aware of what MAtrack has to offer in 'specials'.

Amtrak gives a 10% discount for AAA and for students.

Amtrak is expensive no matter how you do it. If you need to take a break from the costs once in awhile, try the Chinatown buses. They run back and forth between Philly and NYC Chinatowns, with one leaving every hour. It's only $10.

Consider NJ Transit between NYC and Trenton, then pick up SEPTA from Trenton to Philadelphia. On SEPTA you don't have to get off at 30th St. You can get off at Market St. East or the Suburban Station, or other stations along the R7 route.

NJ Transit...my friend said the cheapest would be to pair using NJ Transit and Septa bus.